Vegan nutrition

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Vegan nutrition encompasses the nutrients vegans require for a balanced diet. It is an important part of a vegan's life, as it is the foundation for determining which foods should be consumed based on their lifestyle choices. A balanced vegan diet includes: whole grains, pulses and legumes, a variety of vegetables, nuts and seeds, a variety of fruits, fungi (mushrooms), sea vegetables (laver, arame, kombu) and mineral foods (for a B12 source). There are many vegan food guides available through the American Vegan Society and the Vegetarian Resource Group. Sufficient amounts of all the essential nutrients required for human health are easily obtained from the these guidelines. Vegan nutrition usually refers to the intake and balance of nutrients throughout a day, and therefore is dually classified under dietary regimes and practices.

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Omega-3 fatty acids can be obtained from vegan sources such as hempseed or canola (rapeseed) oils, as well as in walnuts, but these have more omega-6 than omega-3 fats. Dark green leafy vegetables have more omega-3 than omega-6, but the amounts are quite small compared to food oils. Ground flaxseed has much more omega-3 than omega-6. [1] Flaxseed must be ground however, as whole seeds are not broken down in the intestines. Flaxseed oil is best kept in dark bottles and refrigerated to protect it from light and temperature. It should not be heated or used for frying.

There are several vital omega-3 fatty acids. Most vegetable sources contain only Alpha-linolenic acid (ALA). But the human body also requires eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The human body can convert ALA to EPA, and EPA to DHA, but the efficiency, and sufficiency for optimal health, of this conversion is controversial. Studies have found EPA and DHA levels in vegans to be about two thirds lower than in people who eat meat. The extent to which this poses a health risk is not yet known, but vegans have been advised to increase their intake of alpha-linolenic acid, and reduce their intake of omega-6 fatty acids and saturated fatty acids, which can limit the rate of conversion. Recently, some companies have begun to market vegan DHA supplements containing seaweed extracts. Similar supplements providing both DHA and EPA have also begun to appear. Whole seaweeds are not suitable for supplementation because their high iodine content limits the amount that may be safely consumed.

The importance of Omega-3 was highlighted in the "Lyon Diet Heart Study", which found deaths due to heart disease were much lower in a group which followed a Mediterranean diet in comparison to a group following the American Heart Association Diet. The difference between the groups was so large that the study was stopped early by an ethics committee, who found it unethical to continue with so fewer deaths in the Mediterranean group after just one year. The Mediterranean diet emphasizes bread, vegetables, fish, poultry and fruit.[2]

Vegans in countries where the soil is low in iodine, such as the United Kingdom, should ensure they get adequate amounts of this halogen, since dairy products and fish are the most important sources of iodine in these countries. When supplementing the diet with iodine-rich seaweeds such as nori and kelp, moderation is advised, though, because there is a danger of overdosing. Iodized salt may also be used.

Residents of the UK may find themselves iodine-deficient if they rely on local produce, since in the UK iodine is usually obtained via dairy products rather than iodized salt that is more common elsewhere. The Vegan Society says, "Iodine is typically undesirably low (about 50 micrograms/day compared to a recommended level of about 150 micrograms per day) in UK vegan diets unless supplements, iodine rich seaweeds or foods containing such seaweeds are consumed. The low iodine levels in many plant foods reflects the low iodine levels in the UK soil, due in part to the recent ice-age." This demonstrates that location may also be a factor in what deficiencies may be present in any given diet. [3]

The Vegan Society quotes research to show that iron deficiency is no more prevalent in vegans than in the general population (possibly as a result of the higher vitamin C intake of most vegans; vitamin C has been linked to increased iron absorption when taken in conjunction with the source of iron). Vitamin C is the most potent of a list of several known iron enhancers that also includes other organic acids found in fruit and vegetables, as well as sugars. Indeed Vitamin C, can double or triple the amount of iron absorbed when taken with food. Vegans typically have high levels of vitamin C in their diets, which may account for the rarity of anaemia amongst them. In a 1985 Indian study, iron-deficiency anemia in vegetarian children was successfully treated by adding vitamin C to meals. Some consider vegans to be at lower risk of iron deficiency anemia than ovo-lacto-vegetarians because, while eggs are listed as a "fair source" of iron, dairy products contain little and poorly absorbed iron, and both have been found to reduce iron absorption from other food sources consumed at the same time. Other (vegan) foods that may reduce iron absorption are spinach and other high-oxalic acid foods, high-phytic acid foods such as soybeans and unfermented, unsprouted whole-grain cereals, and tannin-rich beverages such as coffee and tea. On the other hand, spinach, soybeans and whole-grain cereals are rich in iron and, when combined with iron enhancers, may constitute good sources of iron. The interaction between iron enhancers and inhibitors in whole foods has not been extensively studied, though.

Vegetarians have been found to have, on the average, normal hemoglobin levels, but lower ferritin levels. On the one hand, this means that vegetarians need a more steady supply of dietary iron, on the other, high ferritin levels have been implied as a risk factor for colorectal cancer and bacterial infections. However, diets lacking in heme-form iron can contribute to anemia and impair performance in endurance athletes (especially females, see menstrual cycle) due to their increased need for hemoglobin in the blood.

Iron is said by the Vegan Society to be present in many typically vegan foodstuffs, including grains, nuts and green leaves. However, the iron in these sources is in a less easily absorbed form (non-heme as opposed to heme iron). Nevertheless, the Vegan Society quotes research to show that iron deficiency is no more prevalent in vegans than in the general population. This research did not account for the fact that many vegans take nutritional supplements that are not found in food alone, whereas other research that excludes this subset of people does indeed show a marked iron deficiency among a majority of those studied. [4]

The American Dietetic Association states that "plant sources of protein alone can provide adequate amounts of essential amino acids if a variety of plant foods are consumed and energy needs are met." Raw nuts and seeds are high in protein.

Frances Moore Lappé's 1971 bestseller Diet for a Small Planet popularized the claim that the protein in plant foods was incomplete and that vegetarians had to "combine" different plant foods (e.g., beans and grains) in order to get a "complete" protein. A decade later in The McDougall Plan (1983) Dr. John McDougall responded that this idea is incorrect and that common plant foods actually contain complete proteins. In The McDougall Program (1990) he wrote, "Nature designed and synthesized our foods complete with all the essential nutrients for human life long before they reach the dinner table. All the essential and nonessential amino acids are represented in single unrefined starches such as rice, corn, wheat, and potatoes in amounts in excess of every individual's needs, even if they are endurance athletes or weight lifters." The World Health Organization standard for protein intake is cited in support of this interpretation. Lappé herself renounced the idea that protein combining was necessary in the 10th edition of Diet for a Small Planet, stating:

With three important exceptions, there is little danger of protein deficiency in a plant food diet. The exceptions are diets very heavily dependent on fruit or on some tubers, such as sweet potatoes or cassava, or on junk food (refined flours, sugars, and fat). Fortunately, relatively few people in the world try to survive on diets in which these foods are virtually the sole source of calories. In all other diets, if people are getting enough calories, they are virtually certain of getting enough protein."

It is wise for vegans and non-vegans alike to avoid trans fats (found in hydrogenated and partially hydrogenated oils), in order to have good nutrition. These transfats are most commonly found in snack food, fried food, and other highly-processed foods. Most fast-food restaurants use hydrogenated oil when cooking their french fries. Partially hydrogenated oils contain the highest proportion of trans-fatty acids. Consumer awareness has recently led to an increased supply of foods such as margarine with no hydrogenated oils. [5]

Vitamin B12, a bacterial product, cannot be reliably found in plant foods, and so vegans are recommended to eat foods with B12 added (such as fortified soy milk, fortified margarines, or many fortified commercial breakfast cereals), certain brands of fortified nutritional yeast[6] (check labels), or take dietary supplements (a good multivitamin will likely include B12 in sufficient quantities).

Some tempeh and some other fermented foods may contain B12 due to bacterial contamination, but cannot be considered reliable sources [7]. Some non-animal organisms (notably seaweeds) and fungi (mushrooms) absorb trace amounts of B12 from growing in bacteria-rich environments. Raw and dried nori, both sometimes touted as vegan B12 sources, have failed tests for B12 activity.[8] No scientific test has yet found a reliable vegetable source (ie. one that works consistently for all testees) of B12. The UK Vegan Society recommends the use of supplements derived from bacteria, and that a minimum of 3μg (micrograms) of B12 be consumed daily.

Inadequate absorption of the body's stores of vitamin B12 poses a health risk, so the vitamin must often be ingested through fortified products and suppliments. Older people—vegan and non-vegan alike—may experience difficulties in absorbing B12 from their food, and anemia (caused by B12 deficiency) is not unknown amongst people who eat meat. B12 deficiency has symptoms such as loss of appetite, fatigue, weakness, dizziness and confusion and can lead to irreversible neurological damage. It is particularly problematic for pregnant women and fetal development, as well as for infants who are breast-fed by a deficient mother.

The Vegan Society concludes:
"...the human need for B12 has increased over time. The longer a vegan does not supplement with B12, the lower their active B12 levels will drop..." [http://www.veganhealth.org/b12/natural

While it would take one to five years to exhaust the body's reserve of vitamin B12, serious health consequences are a very real risk. In a recent laboratory study, 60% of the strict vegan participants' B12 and iron levels were compromised, as compared with the lacto- or lacto-ovo-vegetarian participants (who were able to acquire vitamin B12 from these animal sources). In addition, lower counts of lymphocytes (the white blood cells responsible for immune system responses) and platelets (responsible for blood coagulation) and alterations in the iron metabolism and transport, were demonstrated.

Another B12 study was conducted in rural Africa, partially backed by the U.S. based National Cattlemen's Beef Association, which demonstrated a dramatic improvement in the health of individuals who had, prior to the study, been on diets completely lacking in animal products. The study concluded that the added nutrients, especially vitamin B12 contained in the meat and milk improved the health of the children in the study. The author of the study, Professor Lindsay Allen of the United States Agricultural Research Service, declared: "There's absolutely no question that it's unethical for parents to bring up their children as strict vegans, unless those who practiced them were well-informed about how to add back the missing nutrients through supplements or fortified foods.", and therefore may not be suitable for strict vegans.